438 TT. A. Drusliel — Potassium as the Cobalti-nitrite. 



then filtered through a dry filter into a dry flask. Two 50 cm3 

 portions of the filtrate were transferred with a pipette to plati- 

 num dishes, one portion being" used for the gravimetric estima- 

 tion by the platinum chloride method and the other for the 

 volumetric estimation by the cobalti-nitrite method. After 

 evaporating these portions to half their volume over the steam 

 bath, l cra3 sulphuric acid (1 :1) was added and the evaporation 

 was continued as far as possible over the steam bath, and 

 finally over a low flame. After the danger of spattering was 

 over the flame was increased and the charred organic matter 

 was burned off, finally, over the blast lamp. The potassium 

 sulphate was dissolved by adding a little water and heating 

 over the steam bath, and the potassium was estimated as 

 previously described. 



The volumetric method may be summed up thus: The 

 potassium is precipitated as potassium sodium cobalti-nitrite 

 by an excess of sodium cobalti-nitrite and the mixture is 

 evaporated on the steam bath. The precipitate is separated by 

 filtration through asbestos and oxidized by hot standard potas- 

 sium permanganate. The excess of permanganate is bleached 

 by an excess of standard oxalic acid and the solution is then 

 titrated to color by permanganate. The amount of potassium 

 oxide is found by multiplying the oxygen value of the amount 

 of potassium permanganate used by the factor 1'09. 



This method has the advantages over the platinum chloride 

 method that no expensive reagents are used and that the time 

 required for a determination is materially reduced. The 

 method is considerably shorter than that of Adie and Wood 

 and does not require the potassium solution to be of any 

 definite concentration to work well. 



In closing, the author desires to acknowledge his indebted- 

 ness to Dr. R. G. Yan Name for many helpful suggestions 

 during the progress of the work. 



